This week's book giveaway is in the OCPJP forum. We're giving away four copies of OCA/OCP Java SE 7 Programmer I & II Study Guide and have Kathy Sierra & Bert Bates on-line! See this thread for details.
Minal, Not easily if at all. If you have backups, you can do a restore from there. If not, you can look if there is a tool that can restore files (I don't know if there is one.) Even then, that assumes the file has been overwritten yet.
Yes, Linux file systems aren't like FAT disks. The best thing to do in this case is IMMEDIATELY shut the machine off, and bring it up in single-user mode with the disk containing the deleted file mounted read-only (this may mean booting off of a CD, or even moving the disk to another machine.) Then you can dump the partition with the deleted file using "dd"; now you've got all the remaining data in that dump, and you can reboot the machine normally.
Now, if the deleted file was a text file, you can just search the dump file for some text you know was in the deleted file. If it was something binary, then there are a few programs that can help you examine the dump, depending on what type of file system it was. For an ext2fs partition, there's the "recover" command (Google "Linux recover deleted files").